This invention relates generally to magnetic heads for recording and reproducing information or data on and from a magnetic recording medium, such as a magnetic recording disk or the like, and more particularly, the present invention relates to a perpendicular magnetization recording magnetic head with which magnetization is effected in a direction perpendicular to the plane of a magnetic recording medium.
Perpendicular magnetization recording techniques have been introduced in order to increase the density of information to be recorded or written on a magnetic recording medium. Such a perpendicular magnetization recording method is disclosed, for instance, in U.S. Pat. No. 4,210,946. In a known technique for effecting perpendicular magnetization with respect to a recording medium, a magnetic head having a main pole to be excited is employed for magnetizing a small area on a magnetic recording medium such as a recording disk or sheet. The main pole is constructed of a thin magnetic layer or film made of high permeability material, and a supporter made of a nonmagnetic material in such a manner that the thin magnetic film is sandwiched between a pair of nonmagnetic members constituting the supporter. A coil is wound outside the supporter to thereby construct a magnetic head chip for a main pole extracting type magnetic head. This type of magnetic head is able to record or reproduce information or data from one side of the recording medium in the same manner as a conventional ring type magnetic head, so that the magnetic head is superior for practical use for perpendicular magnetization.
To raise the efficiency of the main pole excited type magnetic head, it is required to increase the amount of interlinkage of the magnetic flux generated from the magnetic medium through the coil wound on the magnetic head. For this reason, it is desirable to lower the magnetic resistance of the magnetic path through the coil. However, in the conventional magnetic head, the magnetic resistance of the magnetic circuit is so relatively high that the recording and reproducing efficiency is low. The high magnetic resistance occurs for the following three reasons.
(1) The thin magnetic layer or film of high permeability material of the main pole is thin (on the order of 1 .mu.m) and long (on the order of several mm).
(2) The magnetic path passes through air which has low permeability in the magnetic circuit established between the high permeability thin magnetic layer or film and high permeability layer of the recording medium.
(3) The high permeability layer of the recording medium has a thickness less than 1 .mu.m and the length of the part thereof constituting the magnetic circuit is in the range of several mm.
As a result, the conventional main pole excited magnetic head for perpendiculer magnetization recording has low recording and reproducing efficiency.
Furthermore, the conventional magnetic head has the drawback of producing low signal to noise ratio because of magnetic flux caused by external noise. That is to say, unnecessary magnetic flux caused by the external noise rush into the main pole and interlink through the coil to be mixed with the signal picked up from the coil.